With the fast development of wireless communication technology, more and more wireless communication devices have been put into use in people's daily lives. Under this background, more and more wireless communication standards have arisen in present spatial environment in pursuit of faster data transfer rate and higher utilization rate of frequency spectrum.
FIG. 1 shows a distribution of frequency spectrum of some communication standards in present spatial environment. For example, mobile communication is one of the most important applications of wireless technology. On the basis of the second generation mobile communication GSM (Global System of Mobile Communication) mode which is widely used currently, mobile communication is now striding into an era of the third generation mobile communication in depth. The third generation mobile communication includes TD-SCDMA of Chinese standard, WCDMA of European standard and CDMA2000 of North American standard. Therefore, wireless signals of different frequencies and different modes which support mobile communication will co-exist for a long term spatially between the second generation mobile communication and the third generation mobile communication as well as between different standards of the third generation mobile communication. In the meantime, as people demands more and more for high speed wireless transmission of data, wireless data communication, especially the wireless wideband data communication technology is developing rapidly. Communication standards that are currently widely used includes Bluetooth and Wi-Fi, and communication standard UWB (Ultra Wideband) having wider band and faster speed in the future, etc. Wireless navigation application is also included. Positioning and navigation system such as GPS (Global Positioning System)/Galileo/BeiDou are also developing rapidly. Broadcasting application is all the more the case. Domestic and international standards such as DTMB (Digital Television Terrestrial Multimedia Broadcasting), CMMB (China Mobile Multimedia Broadcasting), DVB-H (Digital Video Broadcasting-Handheld) and industrial standards are becoming mature or in the process of industrialization advance.
Under the tendency of development of such wireless communication technologies in present days, a wireless receiver which can support multi-standard and multi-mode is especially important, which conforms to the significant tendency of development of radio technology of software-defined radio (SDR) and can greatly improve the reconfigurability of wireless receiver. Therefore, an attempt to propose a radio receiver that supports multi-mode and reconfiguration has been made in the prior art. However, in order to achieve such a radio receiver, the design of a high performance frequency synthesizer with a wideband range is one of the crux; further, a voltage-controlled oscillator (VCO), which can provide the frequency synthesizer with a quadrature local oscillation signal in a wide tuning range (TR) in order to modulate and demodulate wireless signal, is the core of technology.
Currently, in most commercial multi-mode communication devices, a wireless receiver which supports multi-mode typically integrates respective chips of various communication modes into one circuit board. Such a simple stack will lead to increase of power consumption, weight and area of wireless receiver, and the cost will be increased greatly. Therefore, it is a certain tendency that the wireless receiver develops towards the direction of multi-mode and single chip.
In the article entitled “A CMOS 100 MHz to 6 GHz Software Defined Radio Analog Front-end with Integrated Pre-Power Amplifier” to M. Ingets et al (published on ESSCIRC 2007, pages 456-439), a wideband frequency synthesizer is proposed. The frequency synthesizer utilizes a Single Sideband Mixer (SSBM) to perform a upconversion operation to expand frequency band, and utilizes a plurality of Poly Phase Filters (PPF) to provide the Single Sideband Mixer (SSBM) with a quadrature signal; however, in order to improve the operation frequency range of PPF, the number of orders of PPF must be increased, which will necessarily increase power consumption of the frequency synthesizer.
In the article entitled “A 0.75 to 2.2 GHz Continuously-Tunable Quadrature VCO” to M. Ingets et al (published on) to Davide Guermandi et al (published on IEEE ISSCC Digest of Technical Papers, pages 536-537, February, 2005), a wideband frequency synthesizer is proposed. The frequency synthesizer also utilizes a SSBM to perform a upconversion operation to expand frequency band, but utilizes a Quadrature Voltage-Controlled Oscillator (QVCO) to provide the SSBM with a quadrature signal. QVCO, however, has a very limited tuning range, large power consumption and a poor ability in harmonic restraining.
In the article entitled “A 0.1-5 GHz Dual-VCO Software-Defined ΣΔ Frequency Synthesizer in 45 nm Digital CMOS” to Pierluigi Nuzzo et al (published on paper collection “IEEE Radio Frequency Integrated Circuits Symp.”, pages 303-306, June, 2008), a wideband frequency synthesizer is proposed. In this frequency synthesizer, in order to achieve a wide tuning range of voltage-controlled oscillator, two voltage-controlled oscillators which operate in two different frequency bands (high and low) respectively are utilized to cover a very wide tuning range. However, such an architecture demands that the voltage-controlled oscillator operates at a frequency which is two times as big as the required frequency. Then, a mirror is created by Divider(s)-by-2 to refrain the quadrature signal required by the receiver. Due to the use of a high-frequency divider (and also a high-frequency buffer in some cases), the frequency synthesizer of such an architecture has to consume a lot of power in high frequency band, and it is hard to give simultaneous considerations to both the bandwidth and power consumption.